Resistivity Various Materials

Conductors, semiconductors, and insulators are the three types of materials we are familiar with. Conductors are materials that can carry electricity. Before we learn about electrical resistivity in this post, let’s define electrical conductivity and its units. Electrical conductivity is a material’s intrinsic quality that is defined as the measure of how much electrical current it can transport. Specific conductance is another name for electrical conductivity, and the SI unit is Siemens per metre (S/m). It’s also known as the current density to the electric field strength ratio. The Greek letter(σ) is used to signify it.

Electrical resistance

The reciprocal of electrical conductivity is electrical resistivity. It is a measurement of a material’s capacity to resist current flow.

🡺Metals are good electrical conductors. As a result, their resistance is low.

🡺When compared to metallic conductors, insulators such as rubber, glass, graphite, and polymers have an extremely high resistance.

🡺The semiconductor, which sits between conductors and insulators, is the third category. Their resistivity diminishes as the temperature rises, and it is also influenced by the presence of impurities.

Different Materials’ Resistivity

The electrical resistivity of various conductors, semiconductors, and insulators is listed in the table below.

Formula for Resistivity

The resistivity formula for materials with an electric field and current density is:

ρ=E/j

Where,

ρ is the material’s resistivity in Ω.m

E is the electric field’s magnitude in V.m-1.

In A.m-2, j denotes the magnitude of current density.

The resistivity formula for conductors with a uniform cross-section and a uniform flow of electric current is:

ρ=R A/l

Where,

ρ is the material’s resistivity in Ω.m

l is the length of a piece of material in m, and R is the electrical resistance of homogeneous cross-sectional material in R.

A is the material’s cross-sectional area in m2.

Unit of Resistivity

The resistivity unit is as follows:

In CGS the unit of the resistivity is Ω.cm

And the SI unit of the resistivity is Ω.m

Materials Resistivity: Factors to Consider

The following are the elements that influence a material’s resistivity:

Nature and Temperature of the material

Tell us more about resistor colour coding and how to determine the value of a resistor.

Colour coding of the resistor 

In electrical circuits, resistors are used to regulate or reduce the flow of electricity. Electronic colour codes are used to identify their resistance. These resistors have distinct colour bands or rings for different resistance levels.

The resistor colour-coding highlights are as follows:

-It generally has four bands in it.

-The first band represents the resistance’s first important figure.

-The second major figure is the second band. (Sometimes a third band is added for more precision, making them 5 band resistors.)

-The decimal multiplier is the third band.

-The fourth band represents the tolerance (in percentage) with which the resistor can tolerate the specified values.

-In the absence of the fourth band, a tolerance of 20% is used as a default.

The table below shows the values of various colour codes in terms of significant numbers, multiplier, and tolerance.

To further understand resistor colour coding, consider the following example.

The resistor is divided into four colour bands.

The red band is the first. We know that red represents the significant digit 2 because of the table.

Red is the second. The second significant digit 2 is shown by this.

The third ring, which is black, is a multiplier. The multiplier for black is 100or 1.

The fourth band is gold, and it signifies a 5% tolerance.

As a result, the resistor has a resistance of 22 x 1 with a tolerance of 5%.

Factors that influence resistivity

The level of resistivity is also affected by the asset’s temperature; opposing material tables normally establish values at 20 degrees Celsius. Steel conductor resistance often increases as temperature rises, but semiconductor resistance, such as carbon and silicon, typically reduces as temperature rises.

Conductivity is the reciprocal of resistivity and, like resistivity, reflects objects by how well electricity flows through them. The mho metre, or ampere per volt-metre, is the second-kilometre unit of conductivity. Good electrical conductors have a high conductivity and a low resistance. Fine insulators, sometimes known as dielectrics, have a low conductivity and a high resistance. Semiconductors are somewhere in the middle.

Conclusion 

Conductors, semiconductors, and insulators are the three types of materials we are familiar with. Materials that can conduct electricity are known as conductors. Metals are excellent electrical conductors. As a result, their resistance is low. The semiconductor, which sits between conductors and insulators, is the third category. Their resistivity diminishes as the temperature rises, and it is also influenced by the presence of impurities. The reciprocal of electrical conductivity is electrical resistivity. It is a measurement of a material’s capacity to resist current flow.